Base station system and method for call setting up, handing over and releasing in hybrid network

ABSTRACT

A base station system and method for call setting up, handing over and releasing in hybrid network are disclosed. The base station system consists of BSC, TC, several BTSs and a band-width guaranteed IP network. IP mode transport and traditional TDM mode transport between BSC and TC are simultaneity supported in the system, and BTS supports TDM mode or IP mode. The invention provides: compatibility with TDM, which protects the providers&#39; investment; smooth transition from TOM to IP, which decreases investing risk; flexible choice for different physical layer or data link layer transmission apparatuses to bear IP message, which facilitates the providers to constitute their networks. In IP mode, data service can share bandwidth with the mute frames of voice service, the system can coexist with different IP networks, and the control user planes are independent so as to simplify the developing procedure and reduce the maintaining cost.

This application is a division of U.S. patent application Ser. No.12/305,581, filed on Jul. 13, 2009 now U.S. Pat. No. 8,189,534 which isthe national filing of PCT International Application No.PCT/CN2007/001762, filed on Jun. 1, 2007, which claims the benefit ofChinese Application 200610027797.X, filed Jun. 19, 2006.

FIELD OF THE INVENTION

The present invention relates to a base station system (BSS) whichsupports both IP and traditional TDM, and a method for call setting up,handing over and releasing in a hybrid network.

BACKGROUND OF THE INVENTION

Referring to FIG. 1, a traditional BBS (base station subsystem) consistsof a base transceiver station (BTS), a base station controller (BSC), apacket service server (MFS), and a TC (transcoder). It is externallyconnected to a mobile switching center (MSC) through the TC andwirelessly to a mobile terminal (MS) through the BTS. Within thissystem, transmissions are all based on a TDM (time divisionmultiplexing) mode, and there is no distinction between a control planeand a user plane. For the BSC, its external interfaces involve ABISinterfaces from the BTS and Ater interfaces from the TC; for the TC, itsexternal interfaces involve A interfaces with the MSC.

Compared with the traditional TDM network outlined above. IP networksare already well developed and need a low cost for operationmaintenance. Therefore, it is an inevitable trend in thetelecommunication industry that various transmission networks merge intoIP networks.

However, how to cope with issues, such as BIS management in differenttransmission modes, call handover between BTSs operating in differentoperation modes or the like in the course of TDM networks merging intoIP networks, has been a research task to which this industry and theapplicant are denoted.

SUMMARY OF THE INVENTION

The present invention is intended to provide a base station system whichsupports both IP and traditional TDM, and a method for call setting up,handing over and releasing in a hybrid network.

According to a first aspect of the present invention, there is provideda base station controller. The base station controller is connectedbetween several BTSs and a TC under TDM mode, IP/TDM hybrid mode and IPmode, respectively, characterized by comprising an IP/TDM mode call linkcontroller based on a base station controller body, a first signalinginterface controller and a second signaling interface controller eachbeing connected with the IP/TDM mode call link controller, and an IPpackage forwarding unit. Among them, the IP/TDM mode call linkcontroller is used for processing setup, handover and releasing of voiceand data call links during IP transmission or IP/TDM hybridtransmission; the first signaling interface controller is used forprocessing signaling transmission with the TC, controlling setup andreleasing of switch links between voice channels at Ater interfaces andvoice channels at A interfaces inside the TC; the second signalinginterface controller is used for processing signaling and voicetransmission with the BTSs in IP, TDM or IP/TDM hybrid mode, andcontrolling setup and releasing of voice channels between the BTSs andthe TC in IP mode or IP/TDM hybrid mode; the IP package forwarding unitis responsible for forwarding IP packages.

The above-described base station controller further comprises an M2UAlocated inside a signaling No. 7 link controller of the base stationcontroller body and for supporting full IP transmission within thesystem and assuming signaling access of SS7 between the BSC and the TO.

According to a second aspect of the present invention, there is provideda transcoder. The transcoder is used in cooperation with the basestation controller, characterized by comprising a channel transform unitand an IP voice/data frame receiving/sending unit based on a transcoderbody, as well as a signaling No. 7 TDM/IP transform unit connected withthe channel transform unit. Among them, the channel transform unit isused for accepting control signals from the first signaling interfacecontroller of the base station controller and processing link switchbetween various channels at A interfaces and Ater interfaces under IP,TDM or IP/TDM mode; the IP voice/data frame receiving/sending unit isused for accepting control signals from the first signaling interfacecontroller of the base station controller and packing, unpacking,receiving and sending of voice frames under IP transmission mode betweenthe TC and the BTSs; the signaling No. 7 TDM/IP transform unit is usedfor processing the switch of signaling No. 7 between TDM transmissionmode and IP transmission mode.

According to a third aspect of the present invention, there is provideda base transceiver station supporting IP transmission. The basetransceiver station supporting IP transmission comprises a BTS body,characterized by further comprising an IP mode call processing unitbased on the BTS body, an IP voice/data frame receiving/sending unit, aswell as an Ethernet physical interface connected with both the IPvoice/data frame receiving/sending unit and the IP mode call processingunit. Among them, the IP mode call processing unit is used forprocessing setup, handover and releasing of voice call links, under thecontrol of the second signaling interface controller of the BSC; the IPvoice/data frame receiving/sending unit is used for packing, unpacking,receiving and sending of voice frames in IP transmission mode betweenthe TC and the present BTS.

According to a fourth aspect of the present invention there is provideda base transceiver station supporting IP transmission. The basetransceiver station supporting IP transmission comprises a BTS body,characterized by further comprising an IP mode call processing unitbased on the BTS body, an IP voice/data frame receiving/sending unit, aswell as an E1-based IP transport protocol processing unit connected witheach of the IP voice/data frame receiving/sending unit, the IP mode callprocessing unit and an E1 physical interface on the BTS body. Amongthem, the IP mode call processing unit is used for processing setup,handover and releasing of voice call links, under the control of thesecond signaling interface controller of the BSC; the IP voice/dataframe receiving/sending unit is used for packing, unpacking, receivingand sending of voice frames in IP transmission mode between the TC andthe present BTS; the E1-based IP transport protocol processing unit isused for transmitting IP packages between the BTS and the BSC where E1serves as a physical transmission medium.

According to a fifth aspect of the present invention, there is provideda base station system in a hybrid network. The base station systemcomprises the above-described BSC, the above-described TC connected withthe BSC, and several BTSs, wherein it further comprises a bandwidthguaranteed IP network provided among the BSC. TC and BTSs, and IP modetransmission and traditional TDM mode transmission between the BSC andthe TC being simultaneously supported in the system, and wherein theBTSs are either BTSs supporting TDM transmission or BTSs supporting IPtransmission.

In the above-described base station system in a hybrid network, a TCSLprotocol mode is employed for switch link control signaling transmissionbetween the TC and the BSC during IP mode transmission, to set uptraditional TDM transmission at Ater interface in a hybrid network.

In the above-described base station system in a hybrid network, aUDP-based D channel link access protocol mode is employed for signalingtransmission between the BSC and the BTS during IP mode transmission.

In the above-described base station system in a hybrid network, an M2UAprotocol mode is employed for signaling No. 7 transmission between theTC and the BSC.

In the above-described base station system in a hybrid network, aUDP-based TRAUP protocol mode is employed for user plane transmissionbetween the TC and the BTC during IP mode transmission.

According to a sixth aspect of the present invention, there is provideda method of call setup by a base station system in a hybrid networkduring TDM mode-based transmission. The method comprises the followingsteps: upon receipt of a call setup request from an MSC, a TC transformssignaling No. 7 transmitted on the TDM mode basis into signaling No. 7transmitted on the IP mode basis and subsequently forwards signaling No.7 transmitted on the IP mode basis to a BSC; upon receipt of a callsetup request from the TC, the BSC allocates wireless resources, checksa call type, determines the mobile terminal to be located at a TDM-BTS,sends a TC switch link setup request to the TC, sets up a switch linkinside the BSC, and sends a wireless channel allocation request to theBTS; the system's voice channel for TDM mode-based transmission isactivated, whereby an uplink and a downlink are set up.

According to a seventh aspect of the present invention, there isprovided a method of call setup by a base station system in a hybridnetwork during IP mode-based transmission. The method comprises thefollowing steps: upon receipt of a call setup request from an MSC, a TCtransforms signaling No. 7 transmitted on the TDM mode basis intosignaling No. 7 transmitted on the IP mode basis and subsequentlyforwards signaling No. 7 transmitted on the IP mode basis to a BSC; uponreceipt of a call setup request from the TC, the BSC allocates wirelessresources, checks a call type, determines the mobile terminal to belocated at an IP-BTS, and sends a wireless channel allocation request toa BTS; the BTS sends a voice channel connection setup request to the TC;the system's voice channel for IP mode-based transmission is activated,whereby an uplink and a downlink are set up.

According to an eighth aspect of the present invention, there isprovided a method of call handover from TDM-BTS to IP-BTS for a mobileterminal by a base station system in a hybrid network. The methodcomprises the following steps; I) during the procedure of a calltransmitted on the TDM mode basis, a BSC will receive a call handoverrequest triggered by an MSC or inside the BSC; in case of anMSC-triggered call handover request, upon receipt of the call handoverrequest from the MSC, a TC transforms signaling No. 7 transmitted on theTDM mode basis into signaling No. 7 transmitted on the IP mode basis andsubsequently forwards signaling No. 7 transmitted on the IP mode basisto the BSC; the flow then goes to step II); in case of a call handoverrequest triggered inside the BSC, the flow directly goes to step II);II) upon receipt of an internal or external call handover request, theBSC allocates wireless resources, checks a call type, determines themobile terminal to be located at the TDM-BTS, and sends a wirelesschannel allocation request to the IP-BTS; III) the IP-BTS sends a voicechannel connection setup request to the TC; IV) the system's voicechannel for IP mode-based transmission is activated, whereby an uplinkand a downlink are set up; V) the IP-BTS sends an access successindication to the BSC; VI) the BSC sends a TC switch link releasingrequest to the TC, and sends a wireless channel releasing request to theTDM-BTS while releasing its internal switch link.

According to a ninth aspect of the present invention, there is provideda method of call handover from IP-BTS to TDM-BTS for a mobile terminalby a base station system in a hybrid network. The method comprises thefollowing steps: I) during the procedure of a call transmitted on the IPmode basis, a BSC will receive a call handover request triggered by anMSC or inside the BSC; in case of an MSC-triggered call handoverrequest, upon receipt of the call handover request from the MSC, a TCtransforms signaling No. 7 transmitted on the TDM mode basis intosignaling No. 7 transmitted on the IP mode basis and subsequentlyforwards signaling No. 7 transmitted on the IP mode basis to the BSC;the flow then goes to step II); in case of a call handover requesttriggered inside the BSC, the flow directly goes to step II); II) uponreceipt of an internal or external call handover request, the BSCallocates wireless resources, checks a call type, determines the mobileterminal to be located at the IP-BTS, sends a TC switch link setuprequest to the TC while setting up an internal switch link, andsubsequently sends a wireless channel allocation request to the TDM-BTS;III) the TDM-BTS sends a voice channel connection setup request to theTC; IV) the system's voice channel for TDM mode-based transmission isactivated, whereby an uplink and a downlink are set up; V) the TDM-BTSsends an access success indication to the BSC; VI) the BSC sends awireless channel releasing request to the IP-BTS, and the BTS sends aswitch link releasing request to the TC.

According to a tenth aspect of the present invention, there is provideda method of call releasing by a base station system in a hybrid networkduring TDM mode-based transmission. The method comprises the followingsteps: upon receipt of a call releasing request from an MSC, a TCtransforms signaling No. 7 transmitted on the TDM mode basis intosignaling No. 7 transmitted on the IP mode basis and subsequentlyforwards signaling No. 7 transmitted on the IP mode basis to a BSC; uponreceipt of a call releasing request from the TC, the BSC sends awireless channel releasing request to a TDM-BTS and a TC switch linkreleasing request to the TC and releases a switch link inside itself; avoice channel for TDM mode-based transmission is released.

According to an eleventh aspect of the present invent ion, there isprovided a method of call releasing by a base station system in a hybridnetwork during IP mode-based transmission. The method comprises thefollowing steps: upon receipt of a call releasing request from an MSC, aTC transforms signaling No. 7 transmitted on the TDM mode basis intosignaling No. 7 transmitted on the IP mode basis and subsequentlyforwards signaling No. 7 transmitted on the IP mode basis to a BSC; uponreceipt of a call releasing request from the TC, the BSC sends awireless channel releasing request to an IP-BTS; the IP-BTS sends a TCswitch link releasing request to the TC; a voice channel for IPmode-based transmission is released.

With the technical solution described above, the present invention hassuch advantages: compatibility with TDM, which maximumly protects theproviders' investment; smooth transition from TDM to IP, which decreasesinvesting risk; flexible choice for different physical layer or datalayer transmission apparatuses to bear IP messages, which facilitatesthe providers to constitute their networks. In IP mode, data service canshare bandwidth with mute frames which exist in a large number in voiceservice (the priority of data service is lower than that of voiceservice in order to guarantee the voice quality), and the system cancoexist with different IP networks such as 3G or WiMax (worldwidemicrowave access operability). The BSC can be simplified as a signalingserver in a pure IP mode network. And the control plane and the userplane are completely independent of each other so as to simplify thedevelopment procedure and reduce the maintenance cost.

BRIEF DESCRIPTION ON THE DRAWINGS

FIG. 1 is a schematic layout view of a traditional BBS;

FIG. 2 is a schematic layout view of a base station system in a hybridnetwork of the present invention;

FIG. 3 is a processing flowchart of call setup during TDM mode-basedtransmission, which is implemented by a base station system in a hybridnetwork of the present invention;

FIG. 4 is a processing flowchart of call setup during IP mode-basedtransmission, which is implemented by a base station system in a hybridnetwork of the present invention;

FIG. 5( a) is a flowchart of call handover (MSC-triggered call handover)from TDM-BTS to IP-BTS for a mobile terminal, which is implemented by abase station system in a hybrid network of the present invention;

FIG. 5( b) is a flowchart of call handover (call handover triggeredinside a BSC) from TDM-BTS to IP-BTS for a mobile terminal, which isimplemented by a base station system in a hybrid network of the presentinvention;

FIG. 6( a) is a flowchart of call handover (MSC-triggered call handover)from IP-BTS to TDM-BTS for a mobile terminal, which is implemented by abase station system in a hybrid network of the present invention;

FIG. 6( b) is a flowchart of call handover (call handover triggeredinside a BSC) from IP-BTS to TDM-BTS for a mobile terminal, which isimplemented by a base station system in a hybrid network of the presentinvention;

FIG. 7 is a processing flowchart of call releasing during TDM mode-basedtransmission, which is implemented by a base station system in a hybridnetwork of the present invention;

FIG. 8 is a processing flowchart of call releasing during IP mode-basedtransmission, which is implemented by a base station system in a hybridnetwork of the present invention;

FIG. 9 is a schematic layout view of a base station controller of thepresent invention;

FIG. 10 is a schematic layout view of a transcoder of the presentinvention;

FIG. 11( a) is a schematic layout view of a base transceiver station ofthe present invention; and

FIG. 11( b) is another schematic layout view of a base transceiverstation of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIG. 2, the present invention, namely a base station systemin a hybrid network, comprises a BSC, a TC connected with the BSC,several BTSs, and further comprises a bandwidth guaranteed IP networkwhich is provided among the BSC, TC and BTSs. Both IP mode transmissionand traditional TDM mode transmission between the BSC and the TC aresupported in the system, and the BTSs can be either BTSs supporting TDMtransmission or BTSs supporting IP transmission. A detailed descriptionwill be given below to the BSC, TC and BTS, respectively.

I. Base Station Controller (BSC)

As shown in FIG. 9, a base station controller (BSC) is connected betweenseveral BTSs and a TC under TDM mode, IP/TDM hybrid mode and IP mode,respectively, which comprises an IP/TDM mode call link controller 12based on a base station controller body 1, a first signaling interfacecontroller 13 and a second signaling interface controller 11 each beingconnected with IP/TDM mode call link controller 12, and an IP packageforwarding unit 14.

In a breakdown. IP/TDM mode call link controller 12 is used forprocessing setup, handover and releasing of voice and data call linksduring IP transmission or IP/TDM hybrid transmission;

First signaling interface controller 13 is used for processing signalingtransmission with the TC, controlling setup and releasing of switchlinks between voice channels at Ater interfaces and voice channels at Ainterfaces inside the TC;

Second signaling interface controller 11 is used for processingsignaling and voice transmission with the BTSs in IP, TDM or IP/TDMhybrid mode, and controlling setup and releasing of voice channelsbetween the BTSs and the TC in IP mode or IP/TDM hybrid mode;

IP package forwarding unit 14 is responsible for forwarding IP packages.

Further, the base station controller can comprise an M2UA 15 (MTP2 useradaptive layer) located inside a signaling No. 7 link controller of basestation controller body 1 and for supporting full IP transmission withinthe system and assuming signaling access of SS7 between the BSC and theTC.

II. Transcoder (TC)

Referring to FIG. 10, a transcoder (TC) comprises a channel transformunit 22 and an IP voice/data frame receiving/sending unit 23 based on atranscoder body 2, as well as a signaling No. 7 TDM/IP transform unit 21connected with channel transform unit 22.

In a breakdown, channel transform unit 22 is used for accepting controlsignals from first signaling interface controller 13 of the base stationcontroller and processing link switch between various channels at Ainterfaces and Ater interfaces under IP, TDM or IP/TDM mode;

IP voice/data frame receiving/sending unit 23 is used for acceptingcontrol signals from first signaling interface controller 13 of the basestation controller and packing, unpacking, receiving and sending ofvoice frames under IP transmission mode between the TC and the BTSs;

Signaling No. 7 TDM/IP transform unit 21 is used for processing theswitch of signaling No. 7 between TDM transmission mode and IPtransmission mode.

III. Base Transceiver Station (BTS) Supporting IP Transmission

As shown in FIG. 11( a), a BTS which supports IP transmission comprisesa BTS body 3, an IP mode call processing unit 31 based on BTS body 3, anIP voice/data frame receiving/sending unit 32, as well as an Ethernetphysical interface 33 connected with both IP voice/data framereceiving/sending unit 32 and IP mode call processing unit 31.

In a breakdown. IP mode call processing unit 31 is used for processingsetup, handover and releasing of voice call links, under the control ofsecond signaling interface controller 11 of the BSC;

IP voice/data frame receiving/sending unit 32 is used for packing,unpacking, receiving and sending of voice frames in IP transmission modebetween the TC and the present BTS.

As shown in FIG. 11( b), a base transceiver station which supports IPtransmission comprises a BTS body 3′, an IP mode call processing unit31′ based on BTS body 3′, an IP voice/data frame receiving/sending unit32′, as well as an E1-based IP transport protocol processing unit 33′connected with each of IP voice/data frame receiving/sending unit 32′.IP mode call processing unit 31′ and an E1 physical interface 34′ on BTSbody 3′.

In a breakdown, IP mode call processing unit 31′ is used for processingsetup, handover and releasing of voice call links, under the control ofsecond signaling interface controller 11 of the BSC;

IP voice/data frame receiving/sending unit 32′ is used for packing,unpacking, receiving and sending of voice frames in IP transmission modebetween the TC and the present BTS;

E1-based IP transport protocol processing unit 33′ is used fortransmitting IP packages between the BTS and the BSC where E1 serves asa physical transmission medium.

In order to solve the problem concerning IP network-based signalingtransmission for an Abis interface, the above-described base stationsystem in a hybrid network employs a method of carrying a Lapd (Dchannel link access) protocol on UDP, thereby achieving both real-timeperformance and reliability of signaling transmission between the BSCand the BTS. The Abis interface protocol layer is as shown in thefollowing table:

Lapd UDP IP

In order to solve the problem concerning signaling No. 7 transmissionbetween the TC and the BSC, the system employs an M2UA approach, therebyachieving reliable transmission of signaling No. 7 between the TC andthe BSC over IP. The IP-based signaling No. 7 transport protocol layerbetween the TC and the BSC is as shown in the following table:

M2UA SCTP IP

To set up traditional TDM transmission at Atermux (a connect between theBSC and the TC) in a hybrid network, the system employs the existingTCSL protocol, thereby controlling setup and releasing of switch linksbetween A and Atermux on the TC by the BSC and enabling the system tosupport the to traditional TDM mode on Atermux. The IP-based switch linkcontrol protocol layer between the TC and the BSC is as shown in thefollowing table:

TCSL SCTP IP

To solve the problem concerning IP-based user plane transmission betweenthe TC and the BTC, the system employs an existing method of carryingthe TRAUP protocol on UDP, thereby achieving reliable transmission overIP at the user plane between the TC and the BTS. The IP-based user planeprotocol layer between the TC and the BTS is as shown in the followingtable:

TRAUP UDP IP

As shown in FIG. 3, a method of call setup during TDM mode-basedtransmission, which is implemented by the inventive base station systemin a hybrid network, comprises the following steps:

Upon receipt of a call setup request from the MSC, the TC transformssignaling No. 7 transmitted on the TDM mode basis into signaling No. 7transmitted on the IP mode basis and subsequently forwards signaling No.7 transmitted on the IP mode basis to the BSC;

Upon receipt of a call setup request from the TC, the BSC allocateswireless resources, checks a call type, determines the mobile terminalto be located at the TDM-BTS, sends to the TC a TC switch link setuprequest, sets up a switch link inside the BSC, and sends a wirelesschannel allocation request to the BTS;

The system's voice channel for TDM mode-based transmission is activated,whereby an uplink and a downlink are set up.

As shown in FIG. 4, a method of call setup during IP mode-basedtransmission, which is implemented by the inventive base station systemin a hybrid network, comprises the following steps:

Upon receipt of a call setup request from the MSC, the TC transformssignaling No. 7 transmitted on the TDM mode basis into signaling No. 7transmitted on the IP mode basis and subsequently forwards signaling No.7 transmitted on the IP mode basis to the BSC;

Upon receipt of a call setup request from the TC, the BSC allocateswireless resources, checks a call type, determines the mobile terminalto be located at the IP-BTS, and sends a wireless channel allocationrequest to the BTS;

The BTS sends a voice channel connection setup request to the TC;

The system's voice channel for IP mode-based transmission is activated,whereby an uplink and a downlink are set up.

As shown in FIG. 5( a), a method of call handover from TDM-BTS to IP-BTSfor a mobile terminal, which is implemented by the inventive basestation system in a hybrid network, comprises the following steps for anMSC-triggered call handover procedure:

During the procedure of a call transmitted on the TDM mode basis, theBSC will receive an MSC-triggered call handover request. Upon receipt ofa call handover request from the MSC, the TC transforms signaling No. 7transmitted on the TOM mode basis into signaling No. 7 transmitted onthe IP mode basis and subsequently forwards signaling No. 7 transmittedon the IP mode basis to the BSC;

Upon receipt of a call handover request from the outside, the BSCallocates wireless resources, checks a call type, determines the mobileterminal to be located at the TDM-BTS, and sends a wireless channelallocation request to the IP-BTS;

The IP-BTS sends a voice channel connection setup request to the TC;

The system's voice channel for IP mode-based transmission is activated,whereby an uplink and a downlink are set up;

The IP-BTS sends an access success indication to the BSC;

The BSC sends a TC switch link releasing request to the TC, and sends awireless channel releasing request to the TDM-BTS while releasing itsinternal switch link.

As shown in FIG. 5( b), the following steps are comprised for theprocedure of a call handover triggered inside the BSC:

During the procedure of a call transmitted on the TDM mode basis, uponreceipt of a call handover request triggered inside the BSC, the BSCallocates wireless resources, checks a call type, determines the mobileterminal to be located at the TDM-BTS, and sends a wireless channelallocation request to the IP-BTS;

The IP-BTS sends a voice channel connection setup request to the TC;

The system's voice channel for IP mode-based transmission is activated,whereby an uplink and a downlink are set up;

The IP-BTS sends an access success indication to the BSC;

The BSC sends a TC switch link releasing request to the TC, and sends awireless channel releasing request to the TDM-BTS while releasing itsinternal switch link.

As shown in FIG. 6( a), a method of call handover from IP-BTS to TDM-BTSfor a mobile terminal, which is implemented by the inventive basestation system in a hybrid network, comprises the following steps for anMSC-triggered call handover procedure:

During the procedure of a call transmitted on the IP mode basis, the BSCwill receive an MSC-triggered call handover request. Upon receipt of acall handover request from the MSC, the TC transforms signaling No. 7transmitted on the TDM mode basis into signaling No. 7 transmitted onthe IP mode basis and subsequently forwards signaling No. 7 transmittedon the IP mode basis to the BSC;

Upon receipt of a call handover request from the outside, the BSCallocates wireless resources, checks a call type, determines the mobileterminal to be located at the IP-BTS, sends a TC switch link setuprequest to the TC while setting up an internal switch link, andsubsequently sends a wireless channel allocation request to the TDM-BTS;

The TDM-BTS sends a voice channel connection setup request to the TC;

The system's voice channel for TDM mode-based transmission is activated,whereby an uplink and a downlink are set up;

The TDM-BTS sends an access success indication to the BSC;

The BSC sends a wireless channel releasing request to the IP-BTS, andthe BTS sends a switch link releasing request to the TC.

As shown in FIG. 6( b), the following steps are comprised for theprocedure of a call handover triggered inside the BSC:

During the procedure of a call transmitted on the IP mode basis, after acall handover request is triggered inside the BSC, the BSC allocateswireless resources, checks a call type, determines the mobile terminalto be located at the IP-BTS, and sends a TC switch link setup request tothe TC while setting up an internal switch link, and subsequently sendsa wireless channel allocation request to the TDM-BTS;

The TDM-BTS sends a voice channel connection setup request to the TC;

A voice channel for TDM mode-based transmission is activated, whereby anuplink and a downlink are set up;

The TDM-BTS sends an access success indication to the BSC;

The BSC sends a wireless channel releasing request to the IP-BTS, andthe BTS sends a switch link releasing request to the TC.

As shown in FIG. 7, a method of call releasing during TDM mode-basedtransmission, which is implemented by the inventive base station systemin a hybrid network, comprises the following steps:

Upon receipt of a call releasing request from the MSC, the TC transformssignaling No. 7 transmitted on the TDM mode basis into signaling No. 7transmitted on the IP mode basis and subsequently forwards signaling No.7 transmitted on the IP mode basis to the BSC;

Upon receipt of a call releasing request from the TC, the BSC sends awireless channel releasing request to the TDM-BTS and a TC switch linkreleasing request to the TC and releases a switch link inside itself;

The system's voice channel for TDM mode-based transmission is released.

As shown in FIG. 8, a method of call releasing during IP mode-basedtransmission, which is implemented by the inventive base station systemin a hybrid network, comprises the following steps:

Upon receipt of a call releasing request from the MSC, the TC transformssignaling No. 7 transmitted on the TDM mode basis into signaling No. 7transmitted on the IP mode basis and subsequently forwards signaling No.7 transmitted on the IP mode basis to the BSC;

Upon receipt of a call releasing request from the TC, the BSC sends awireless channel releasing request to the IP-BTS;

The IP-BTS sends a TC switch link releasing request to the TC;

The system's voice channel for IP mode-based transmission is released.

To sum up, fundamental ideas of the present invention comprise thefollowing:

1. To protect the investment of providers, the impact on existingnetworks should be minimized. Since main devices and transmissionresources are at Abis in BBS systems, this solution gives priority tothe reduction of impact on Abis.

2. New networks should be compatible with prior TDM mode. BTSs and TCwhich operate in TDM mode and cannot be updated to IP mode (due to thememory, CPU and other restrictions) should be supported still.

3. For BTSs which need to be updated to IP mode, it is possible withIPoE1 that original E1 transmission links need no alteration. Providerscan switch a mode of BTSs at any time (TDM->IP, IP->TDM).

4. New transmission mode (Ethernet, xDSL . . . ) interfaces are providedfor new BTSs, thereby making full use of IP advantages.

5. For a connection between the BSC and the TC, the network supportsboth IP and traditional TDM mode, so that providers can protect originaltransmission resources to the greatest extent.

6. For a connection between the BSC and the TC, since it is close to thecore network and needs a lower cost for transformation, it can be deemedin principle that a bandwidth guaranteed IP network can be providedbetween the BSC and the TC. Additionally, if providers wish to utilizeoriginal transmission networks and TC resources, traffic still can becarried over E1 in TDM mode. Since all signaling (SS7) will use IP mode,a new TC should provide an interface to the IP network.

It should be noted that the technical solution of the present inventionhas been presented for purposes of illustration only and not in alimiting sense. While the present invention has been described withreference to the embodiments, it is understood by those of ordinaryskill in the art that modification or equivalent arrangements can bemade to the present invention. The scope of the claims is to encompassany modifications or partial arrangements included within the spirit andscope of the present invention.

What is claimed is:
 1. A base transceiver station which supportsInternet Protocol (IP) transmission, comprising a base transceiverstation (BTS) body, an IP mode call processing unit based on the BTSbody, an IP voice/data frame receiving/sending unit, and an Ethernetphysical interface connected with both the IP voice/data framereceiving/sending unit and the IP mode call processing unit, wherein theIP mode call processing unit is configured for processing setup,handover and releasing of voice call links, under the control of asignaling interface controller of a base station controller (BSC); theIP voice/data frame receiving/sending unit is configured for packing,unpacking, receiving and sending of voice frames in IP transmission modebetween a transcoder (TC) and the present BTS.
 2. A base transceiverstation which supports Internet Protocol (IP) transmission, comprising abase transceiver station (BTS) body, an IP mode call processing unitbased on the BTS body, an IP voice/data frame receiving/sending unit,and an E1-based IP transport protocol processing unit connected witheach of the IP voice/data frame receiving/sending unit, the IP mode callprocessing unit and an E1 physical interface on the BTS body, whereinthe IP mode call processing unit is configured for processing setup,handover and releasing of voice call links, under the control of asignaling interface controller of a base station controller (BSC); theIP voice/data frame receiving/sending unit is configured for packing,unpacking, receiving and sending of voice frames in IP transmission modebetween a transcoder (TC) and the present BTS; the E1-based IP transportprotocol processing unit is configured for transmitting IP packagesbetween the BTS and the BSC where E1 serves as a physical transmissionmedium.
 3. The base station of claim 2, wherein a User Datagram Protocol(UDP)-based D channel link access protocol mode is employed forsignaling transmission between the BSC and the BTS during IP modetransmission.
 4. The base station of claim 2, wherein an MessageTransfer Part Level 2 User Adaptation Layer (M2UA) protocol mode isemployed for signaling No. 7 transmission between the TC and the BSC. 5.The base station of claim 2, wherein a User Datagram Protocol(UDP)-based protocol mode is employed for user plane transmissionbetween the TC and the BTC during IP mode transmission.